U.S. patent application number 12/690870 was filed with the patent office on 2011-07-21 for high-efficiency all-digital transmitter.
Invention is credited to Richard W. D. Booth, Gregoire Ie Grand de Mercey, Paul Cheng-Po Liang, Toru Matsuura, Koji Takinami, Hua Wang.
Application Number | 20110176636 12/690870 |
Document ID | / |
Family ID | 44277584 |
Filed Date | 2011-07-21 |
United States Patent
Application |
20110176636 |
Kind Code |
A1 |
Wang; Hua ; et al. |
July 21, 2011 |
HIGH-EFFICIENCY ALL-DIGITAL TRANSMITTER
Abstract
A low cost high-efficiency all-digital transmitter using
all-digital power amplifiers ("DPA") and various mapping techniques
to generate an output signal, which substantially reproduces a
baseband signal at a carrier frequency. A baseband signal generator
generates a baseband signal which is quantized by a signal
processor using a quantization map. A DPA control mapper outputs
control signals to phase selectors using the quantized signal and a
quantization table. Each phase selector receives one of the control
signals and outputs a waveform at a carrier frequency with a phase
corresponding to the control signals, or an inactive signal. Each
DPA in a DPA array has an assigned weight, receives one of the
waveforms from the phase selectors, and outputs a power signal
according to the weight of the DPA and the phase of the received
waveform. The combined power signal substantially reproduces the
baseband signal at the carrier frequency.
Inventors: |
Wang; Hua; (San Jose,
CA) ; Matsuura; Toru; (Osaka, JP) ; Ie Grand
de Mercey; Gregoire; (San Jose, CA) ; Liang; Paul
Cheng-Po; (Santa Clara, CA) ; Takinami; Koji;
(Saratoga, CA) ; Booth; Richard W. D.; (San Jose,
CA) |
Family ID: |
44277584 |
Appl. No.: |
12/690870 |
Filed: |
January 20, 2010 |
Current U.S.
Class: |
375/302 |
Current CPC
Class: |
H03D 7/165 20130101;
H04L 27/36 20130101 |
Class at
Publication: |
375/302 |
International
Class: |
H04L 27/12 20060101
H04L027/12 |
Claims
1. A transmitter comprising: a signal processor for receiving a
baseband signal and generating a quantized signal; a mapper for
receiving the quantized signal and generating a plurality of
control signals; a phase selection array for receiving the
plurality of control signals and generating a plurality of
waveforms at a carrier frequency having a phase selected from
multiple possible phases; and a digital power amplifier array for
receiving the plurality of waveforms at the carrier frequency and
generating an output signal.
2. The transmitter of claim 1 wherein the digital power amplifier
array comprises a plurality of digital power amplifiers each
receiving one of the plurality of waveforms at the carrier
frequency and generating a power signal.
3. The transmitter of claim 2 further comprising a combiner for
combining the plurality of power signals to generate the output
signal.
4. The transmitter of claim 1 wherein the phase selection array
comprises an oscillator generating multiple phase signals, and a
plurality of phase selectors, each of the phase selectors receiving
the multiple phase signals and one of the plurality of control
signals, and either outputting an inactive signal, or one of the
waveforms at the carrier frequency having a phase corresponding to
one of the multiple phase signals, based on the one of the
plurality of control signals.
5. The transmitter of claim 1 wherein the signal processor
generates the quantized signal using a quantization map.
6. The transmitter of claim 5 wherein the quantization map is an
equal-weight quantization map.
7. The transmitter of claim 5 wherein the quantization map is a
binary-weight quantization map.
8. The transmitter of claim 5 wherein the quantization map is an
arbitrary-weight quantization map.
9. The transmitter of claim 1 wherein the mapper generates the
plurality of control signals using a quantization table.
10. The transmitter of claim 9 wherein the quantization table is an
equal-weight quantization table.
11. The transmitter of claim 9 wherein the quantization table is a
binary-weight quantization table.
12. The transmitter of claim 9 wherein the quantization table is an
arbitrary-weight quantization table.
13. A transmitter comprising: a signal processor for receiving a
baseband signal and generating a first quantized signal and a
second quantized signal; a mapper for receiving the first quantized
signal and the second quantized signal and generating a first
plurality of control signals and a second plurality of control
signals; a first phase selection array for receiving the first
plurality of control signals and generating a first plurality of
waveforms at a carrier frequency having a phase selected from
multiple possible phases; a second phase selection array for
receiving the second plurality of control signals and generating a
second plurality of waveforms at the carrier frequency having a
phase selected from multiple possible phases; and a digital power
amplifier array for receiving the first plurality of waveforms at
the carrier frequency and the second plurality of waveforms at the
carrier frequency, and generating an output signal.
14. The transmitter of claim 13 wherein the digital power amplifier
array comprises a first plurality of digital power amplifiers each
receiving one of the first plurality of waveforms at the carrier
frequency and generating a power signal, a second plurality of
digital power amplifiers each receiving one of the second plurality
of waveforms at the carrier frequency and generating a power
signal, and a combiner for combining the plurality of power signals
from the first plurality of digital power amplifiers and the second
plurality of digital power amplifiers to generate the output
signal.
15. The transmitter of claim 13 further comprising: an oscillator
connected to the first phase selection array and the second phase
selection array, the oscillator generating multiple phase signals,
and wherein the first phase selection array includes a first
plurality of phase selectors, each of the first plurality of phase
selectors receiving the multiple phase signals and one of the first
plurality of control signals, and either outputting an inactive
signal, or one of the first plurality of waveforms at the carrier
frequency having a phase corresponding to one of the multiple phase
signals, based on the one of the first plurality of control
signals, and the second phase selection array includes a second
plurality of phase selectors, each of the second plurality of phase
selectors receiving the multiple phase signals and one of the
second plurality of control signals, and either outputting an
inactive signal, or one of the second plurality of waveforms at the
carrier frequency having a phase corresponding to one of the
multiple phase signals, based on the one of the second plurality of
control signals.
16. The transmitter of claim 15 wherein the multiple phase signals
are orthogonal multiple phase signals.
17. The transmitter of claim 13 wherein the signal processor
generates the quantized signal using a quantization map.
18. The transmitter of claim 17 wherein the quantization map is an
equal-weight quantization map.
19. The transmitter of claim 17 wherein the quantization map is a
binary-weight quantization map.
20. The transmitter of claim 17 wherein the quantization map is an
arbitrary-weight quantization map.
21. The transmitter of claim 17 wherein the quantization map is a
grid quantization map.
22. The transmitter of claim 13 wherein the mapper generates the
plurality of control signals using a quantization table.
23. The transmitter of claim 22 wherein the quantization table is
an equal-weight quantization table.
24. The transmitter of claim 22 wherein the quantization table is a
binary-weight quantization table.
25. The transmitter of claim 22 wherein the quantization table is
an arbitrary-weight quantization table.
26. The transmitter of claim 22 wherein the quantization table is a
grid quantization table.
27. A method for generating an output signal in a transmitter
comprising: receiving a baseband signal; generating from the
baseband signal, a quantized signal; generating from the quantized
signal, a plurality of control signals; generating from the
plurality of control signals, a plurality of waveforms at a carrier
frequency having a phase selected from multiple possible phases;
and generating from the plurality of waveforms at the carrier
frequency, an output signal.
28. The method of claim 27 further comprising generating a power
signal for each of the plurality of waveforms at the carrier
frequency, and combining the plurality of power signals to generate
the output signal.
29. The method of claim 27 wherein the step of generating from the
plurality of control signals, a plurality of waveforms at a carrier
frequency having a phase selected from multiple possible phases
includes generating multiple phase signals, and either outputting
an inactive signal, or one of the waveforms at the carrier
frequency having a phase corresponding to one of the plurality
control signals and one of the multiple phase signals.
30. The method of claim 27 wherein the step of generating the
quantized signal includes generating the quantized signal using a
quantization map.
31. The method of claim 30 wherein the quantization map is an
equal-weight quantization map.
32. The method of claim 30 wherein the quantization map is a
binary-weight quantization map.
33. The method of claim 30 wherein the quantization map is an
arbitrary-weight quantization map.
34. The method of claim 27 wherein the step of generating the
plurality of control signals includes generating the control
signals using a quantization table.
35. The method of claim 34 wherein the quantization table is an
equal-weight quantization table.
36. The method of claim 34 wherein the quantization table is a
binary-weight quantization table.
37. The method of claim 34 wherein the quantization table is an
arbitrary-weight quantization table.
Description
BACKGROUND
[0001] 1. Field of the Invention
[0002] The present invention relates to a high-efficiency
all-digital transmitter.
[0003] 2. Description of Related Art
[0004] High-efficiency transmitters are preferred in wireless
communications because they allow longer talk time and/or longer
battery life. Conventional high-efficiency transmitter may use, for
example, polar modulation schemes. However, polar domain signal
processing and supply modulation in the polar modulation scheme use
two separate paths to a power amplifier, an amplitude modulation
("AM") path and a phase modulation ("PM") path. The AM path and the
PM path have delay mismatch problems to the power amplifier, which
can make it difficult to build a supply modulator required for the
AM path. Thus, it is difficult to implement a supply modulator,
which has high bandwidth, low noise, and high efficiency.
Therefore, production of the conventional high efficiency
transmitters is costly.
[0005] Thus, there is a need for a low cost high-efficiency
all-digital transmitter.
SUMMARY OF THE INVENTION
[0006] The present invention is directed to a low cost
high-efficiency all-digital transmitter which uses all-digital
power amplifiers. The present invention uses various mapping
techniques to generate an output signal, which substantially
reproduces a baseband signal at a carrier frequency. The various
mapping techniques can be, for example, equal-weight mapping,
binary-weight mapping, arbitrary weight mapping, and/or grid
mapping. In the present invention, a baseband signal generator
generates a baseband signal which is quantized by a signal
processor using a quantization map specific to the selected mapping
technique. The digital power amplifier ("DPA") control mapper
outputs control signals to a phase selection array using the
quantized signal and its corresponding entry in a quantization
table. The quantization table corresponds to the quantization map
and is also specific to the selected mapping technique. The phase
selector array comprises multiple phase selectors, with each phase
selector receiving one of the control signals. Each of the phase
selectors either outputs a waveform at a carrier frequency with a
phase corresponding to the control signals or outputs an inactive
signal. The possible phases for the phase selectors can be
increased to reduce the noise for the output signal.
[0007] A DPA array comprises a plurality of DPAs with each of the
DPAs having an assigned weight according to the mapping technique.
The number of phase selectors and the number of DPAs can correspond
in a one to one manner. Increasing the number of phase selectors
and DPAs used can reduce the noise of output signal. Each of the
DPAs receives one of the waveforms from the phase selectors and
outputs a power signal according to the weight of the DPA and the
phase of the received waveform. The combined power signal
substantially reproduces the baseband signal at the carrier
frequency. Thus, the present invention can reproduce the baseband
signal at the carrier frequency without using supply modulation and
without mismatch problems. This can reduce the production cost of
the transmitters.
[0008] In one embodiment, the present invention is a transmitter
including a signal processor for receiving a baseband signal and
generating a quantized signal using a quantization map, a mapper
for receiving the quantized signal and generating a plurality of
control signals using a quantization table, a phase selection array
for receiving the plurality of control signals and generating a
plurality of waveforms at a carrier frequency having a phase
selected from multiple possible phases, and a digital power
amplifier array for receiving the plurality of waveforms at the
carrier frequency and generating an output signal.
[0009] In another embodiment, the present invention is a
transmitter including a signal processor for receiving a baseband
signal and generating a first quantized signal and a second
quantized signal using a quantization map, a mapper for receiving
the first quantized signal and the second quantized signal and
generating a first plurality of control signals and a second
plurality of control signals using a quantization table, a first
phase selection array for receiving the first plurality of control
signals and generating a first plurality of waveforms at a carrier
frequency having a phase selected from multiple possible phases, a
second phase selection array for receiving the second plurality of
control signals and generating a second plurality of waveforms at
the carrier frequency having a phase selected from multiple
possible phases, and a digital power amplifier array for receiving
the first plurality of waveforms at the carrier frequency and the
second plurality of waveforms at the carrier frequency, and
generating an output signal.
[0010] In another embodiment, the present invention is a method for
generating an output signal in a transmitter including receiving a
baseband signal, generating from the baseband signal, a quantized
signal using a quantization map, generating from the quantized
signal, a plurality of control signals using a quantization table,
generating from the plurality of control signals, a plurality of
waveforms at a carrier frequency having a phase selected from
multiple possible phases, and generating from the plurality of
waveforms at the carrier frequency, an output signal.
BRIEF DESCRIPTION OF THE DRAWINGS
[0011] The objects and features of the present invention, which are
believed to be novel, are set forth with particularity in the
appended claims. The present invention, both as to its organization
and manner of operation, together with further objects and
advantages, may best be understood by reference to the following
description, taken in connection with the accompanying
drawings.
[0012] FIG. 1 is a schematic diagram of a transmitter according to
an embodiment of the present invention;
[0013] FIG. 2 is a schematic diagram of a transmitter according to
an embodiment of the present invention;
[0014] FIG. 3 is a schematic diagram of a combiner according to an
embodiment of the present invention;
[0015] FIG. 4 is a schematic diagram of a multi-phase oscillator,
phase selectors, and digital power amplifiers according to an
embodiment of the present invention;
[0016] FIG. 5 is a map of a segment for an equal-weight
quantization map;
[0017] FIG. 6 is a map of an equal-weight quantization map; and
[0018] FIG. 7 is a map of an equal-weight quantization map
including a quantization point according to an embodiment of the
present invention;
[0019] FIG. 8 is a map of a segment for an equal-weight
quantization map including a quantization point according to an
embodiment of the present invention;
[0020] FIG. 9 is a process according to an embodiment of the
present invention;
[0021] FIG. 10 is a control signal table according to an embodiment
of the present invention;
[0022] FIG. 11 is a portion of an equal-weight quantization table
according to an embodiment of the present invention;
[0023] FIG. 12 is a map of a segment for an equal-weight
quantization map according to an embodiment of the present
invention;
[0024] FIG. 13 is a portion of an equal-weight quantization table
according to an embodiment of the present invention;
[0025] FIG. 14 is a map of an equal-weight quantization map
according to an embodiment of the present invention;
[0026] FIG. 15 is a portion of an equal-weight quantization table
according to an embodiment of the present invention;
[0027] FIG. 16 is a map of an equal-weight quantization map
according to an embodiment of the present invention;
[0028] FIG. 17 is a PSD graph for an output signal of a transmitter
according to an embodiment of the present invention;
[0029] FIG. 18 is a schematic diagram of a multi-phase oscillator,
phase selectors, and digital power amplifiers according to an
embodiment of the present invention;
[0030] FIG. 19 is a map of a segment for a binary-weight
quantization map according to an embodiment of the present
invention;
[0031] FIG. 20 is a map of a binary-weight quantization map
according to an embodiment of the present invention;
[0032] FIG. 21 is a map of a binary-weight quantization map
including a quantization point according to an embodiment of the
present invention;
[0033] FIG. 22 is a map of a segment for a binary-weight
quantization map including a quantization point according to an
embodiment of the present invention;
[0034] FIG. 23 is a control signal table according to an embodiment
of the present invention;
[0035] FIG. 24 is a portion of a binary-weight quantization table
according to an embodiment of the present invention;
[0036] FIG. 25 is a map of a segment for a binary-weight
quantization map according to an embodiment of the present
invention;
[0037] FIG. 26 is a portion of a binary-weight quantization table
according to an embodiment of the present invention;
[0038] FIG. 27 is a map of a segment for a binary-weight
quantization map according to an embodiment of the present
invention;
[0039] FIG. 28 is a portion of a binary-weight quantization table
according to an embodiment of the present invention;
[0040] FIG. 29 is a map of a segment for a binary-weight
quantization map according to an embodiment of the present
invention;
[0041] FIG. 30 is a schematic diagram of an oscillator, phase
selectors, and digital power amplifiers according to an embodiment
of the present invention;
[0042] FIG. 31 is a map of a segment for an arbitrary-weight
quantization map according to an embodiment of the present
invention;
[0043] FIG. 32 is a map of an arbitrary-weight quantization map
according to an embodiment of the present invention;
[0044] FIG. 33 is a map of an arbitrary-weight quantization map
including a quantization point according to an embodiment of the
present invention;
[0045] FIG. 34 is a map of a segment for an arbitrary-weight
quantization map including a quantization point according to an
embodiment of the present invention;
[0046] FIG. 35 is a control signal table according to an embodiment
of the present invention;
[0047] FIG. 36 is a portion of an arbitrary-weight quantization
table according to an embodiment of the present invention;
[0048] FIG. 37 is a map of a segment for an arbitrary-weight
quantization map according to an embodiment of the present
invention;
[0049] FIG. 38 is a portion of an arbitrary-weight quantization
table according to an embodiment of the present invention;
[0050] FIG. 39 is a map of a segment for an arbitrary-weight
quantization map according to an embodiment of the present
invention;
[0051] FIG. 40 is a portion of an arbitrary-weight quantization
table according to an embodiment of the present invention;
[0052] FIG. 41 is a map of a segment for an arbitrary-weight
quantization map according to an embodiment of the present
invention;
[0053] FIG. 42 is a schematic diagram of a transmitter according to
another embodiment of the present invention;
[0054] FIG. 43 is a map of a grid quantization map according to an
embodiment of the present invention;
[0055] FIG. 44 is a control signal table according to an embodiment
of the present invention;
[0056] FIG. 45 is a portion of a grid quantization table according
to an embodiment of the present invention;
[0057] FIG. 46 is a control signal table according to an embodiment
of the present invention;
[0058] FIG. 47 is a portion of a grid quantization table according
to an embodiment of the present invention; and
[0059] FIG. 48 is a PSD graph for a transmitter according to an
embodiment of the present invention.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0060] Reference will now be made in detail to the preferred
embodiments of the invention which set forth the best modes
contemplated to carry out the invention, examples of which are
illustrated in the accompanying drawings. While the invention will
be described in conjunction with the preferred embodiments, it will
be understood that they are not intended to limit the invention to
these embodiments. On the contrary, the invention is intended to
cover alternatives, modifications and equivalents, which may be
included within the spirit and scope of the invention as defined by
the appended claims. Furthermore, in the following detailed
description of the present invention, numerous specific details are
set forth in order to provide a thorough understanding of the
present invention. However, it will be obvious to one of ordinary
skill in the art that the present invention may be practiced
without these specific details. In other instances, well known
methods, procedures, components, molding procedures have not been
described in detail as not to unnecessarily obscure aspects of the
present invention.
[0061] As seen in FIG. 1 the present invention can include a
transmitter 100, a high power output unit 112, and/or a low power
output unit 114. The transmitter 100 can be, for example, a
transmitter in an electronic device, such as a mobile phone. The
transmitter 100 can receive, for example, an input signal and
generate an output signal at a carrier frequency. The output signal
can optionally be transmitted to a high power output unit 112
and/or a lower power output unit 114. The high power output unit
112 can be, for example, a front end module unit 112, and can
include switches 122, and an antenna 124. The low power output unit
114 can be, for example, an external power amplifier and can
include a power amplifier 126. The power amplifier 126 can be, for
example, a linear power amplifier 126. The transmitter 100
includes, for example, a baseband IQ signal generator 102, a signal
processor 104, a digital power amplifier ("DPA") control mapper
106, a phase selection array 108, and/or a DPA array 110.
[0062] The baseband IQ signal generator 102 receives an input
signal and generates baseband signals, such as I_bb, and Q_bb. I_bb
is the "I" component of the baseband signal while Q_bb is the "Q"
component of the baseband signal. The signal processor 104 receives
the I_bb and Q_bb signals and generates the quantized signals I_sp
and Q_sp using, for example, a quantization map, which will be
explained later. The DPA control mapper ("DCM") 106 receives the
quantized signals I_sp and Q_sp, and generates control signals C_1
through C_n corresponding to the quantized signals using, for
example, a quantization table, which will be explained later. In
one embodiment, n can be any integer corresponding to a number of
phase selectors in the phase selection array 108. The number of
phase selectors in the phase selection array 108 can, for example,
correspond to a number of DPAs in the DPA array 110.
[0063] The phase selection array 108 receives the control signals
and generates a plurality of waveforms at a carrier frequency
having a phase selected from multiple possible phases. The phase of
each of the waveforms is determined, for example, by a
corresponding control signal. For example, the phase selection
array 108 can include an oscillator 115 and/or a plurality of phase
selectors 116. The oscillator 115 can generate multiple phase
signals which are fed to each of the phase selectors 116. The
oscillator 115 can also be separate from the phase selection array
108. Each of the phase selectors 116 receives one of the control
signals C_1 through C_n and the multiple phase signals. For
example, one of the phase selectors 116 can receive the control
signal C_1, while another one of the phase selectors 116 can
receive the control signal C_n. Based on the control signal that
each of the phase selectors 116 receives, the individual phase
selector can output either an inactive signal or a waveform with a
phase corresponding to one of the multiple phase signals, which
will be explained in more detail later.
[0064] The DPA array 110 receives the plurality of waveforms at the
carrier frequency and generates an output at a carrier frequency
from the plurality of waveforms. The DPA array 110 can include a
plurality of DPAs 118 and a combiner 120. Each of the plurality of
DPAs 118 can operate in a compressed mode allowing for the DPAs 118
to operate at a high efficiency. Furthermore, each of the plurality
of DPAs 118 outputs a power signal with a phase and a gain
according to an assigned weight. The phase is the phase of the
waveform received by the single DPA 118. Each of the plurality of
DPAs 118 has a predetermined weight, which determines a magnitude
of a power signal output by the single DPA 118 relative to other
power signals. Thus, each of the plurality of DPA 118 receives one
of the plurality of waveforms and generates a power signal with the
phase of the waveform and the weight of the DPA. The combiner
combines the power signals to generate the output at the carrier
frequency. The output approximates the baseband signals I_bb and
Q_bb at the carrier frequency.
[0065] FIG. 2 depicts the transmitter 200 according to an
embodiment of the present invention. The transmitter 200 includes
more specific components for the signal processor 104. The
transmitter 200 outputs an output signal v(t) at a carrier
frequency. Generally the output signal v(t) should approximate the
baseband signals I_bb and Q_bb, but at the carrier frequency. In
the transmitter 200, the signal processor 104 includes a noise
shaper 128 and a quantizer 130. The noise shaper 128 receives the
baseband signals I_bb and Q_bb and shapes their noises to generate
the signals I_ns and Q_ns, which are transmitted to the quantizer
130. The quantizer 130 uses a quantization map to quantize the
signals I_ns and Q_ns to generate the quantized signals
I_.DELTA..SIGMA. and Q_.DELTA..SIGMA., which will be explained
later. I_.DELTA..SIGMA. and Q_.DELTA..SIGMA. are signals which have
been signal processed using .DELTA..SIGMA. processing and which
have further been quantized to approximate the baseband signals
I_bb and Q_bb. The quantizer 130 can also have a feedback loop to
the noise shaper 128. In FIG. 2, the noise shaper 128 and the
quantizer 130 can form, for example, a .DELTA..SIGMA.
converter.
[0066] In FIG. 2, the oscillator 115 is separate from the phase
selection array 108. Furthermore, the oscillator 115 can be, for
example, a voltage controlled oscillator ("VCO") and/or a
multi-phase oscillator. The oscillator 115 can produce a plurality
of phases. In one embodiment, the oscillator 115 can also produce a
single phase at a high frequency. In such a case, a divider can
also be used in conjunction with the oscillator 115 to produce the
plurality of phases. Also, the DPA array 110 is shown by its
components, the plurality of DPAs 118 and the combiner 120. The
combiner 120 can be seen in FIG. 3. The combiner 120 can include a
plurality of capacitors 134 having varying capacitive values. The
outputs of the capacitors 134 are fed into an inductor 136
connected in series with a resistor 138. The output 140 is taken
between the inductor 136 and the resister 138. The output 140 is
the output signal v(t) at carrier frequency such that
v(t)=I_.DELTA..SIGMA.(t)cos(.omega..sub.ct)-Q_.DELTA..SIGMA.(t)sin(.omega-
..sub.ct). I_.DELTA..SIGMA. and Q_.DELTA..SIGMA. are quantized
approximations of I_bb and Q_bb and thus
I_.DELTA..SIGMA.(t)cos(.omega..sub.ct)-Q_.DELTA..SIGMA.(t)sin(.omega..sub-
.ct) are quantized approximations of baseband signals I_bb and Q_bb
at the carrier frequency.
[0067] Referring back to FIGS. 1 and 2, the quantization map used
by the signal processor 104 and/or the quantizer 130 can depend on
a type of mapping technique performed. For example, the present
invention can use equal-weight mapping, binary-weight mapping,
arbitrary-weight mapping, grid mapping, and/or any other types of
mapping which can improve a performance of a transmitter or reduce
an implementation cost of a transmitter. The performance
improvement can be, for example, an increase in signal-to-noise
ratio and/or an efficiency of the transmitter.
[0068] In one embodiment, as shown in FIG. 4, six phase selectors
116a-116f and six DPAs 118a-118f are used for the equal-weight
mapping. Although six phase selectors 116 and six DPAs 118 are
shown in FIG. 4, the number of phase selectors 116 and the number
of DPAs are merely illustrative. Thus, any number of phase
selectors 116 and any number of DPAs 118 may be used. Furthermore,
each of the DPAs 118a-118f has its weight displayed in parenthesis.
In equal-weight mapping, the weight of each DPA is equal to each
other as can be seen by each of the DPAs 118a-118f in FIG. 4 having
a weight of "1."
[0069] When using equal-weight mapping, an equal-weight
quantization map should be utilized. To generate an equal-weight
quantization map, a first segment of the equal-weight quantization
map is generated as shown in FIG. 5. For equal-weight mapping, each
of the DPAs 118a-118f have an equal weight, such as "1."
Furthermore, each of the DPAs 118a-118f can be inactive, output a
power signal at carrier frequency with a 0.degree. phase and a
weight of "1", or output a power signal with a multiple of a
.theta. phase and a weight of "1". In FIG. 5, .theta. is set to be
45.degree., however, the .theta. can be set at any angle. By
increasing the number of DPAs 118 used or reducing the .theta.
used, the noise in the power spectral density ("PSD") can be
reduced because the number of quantization points is increased. The
increase in the number of quantization points reduces noise and PSD
since the Euclidian distance between the closest quantization point
(I_.DELTA..SIGMA. and Q_.DELTA..SIGMA.) and the noise shaped
baseband signal (I_ns and Q_ns) is generally decreased. This can
improve an approximation of the baseband signal (I_bb and
Q_bb).
[0070] As seen in FIG. 5, all combinations of the states of the
DPAs 118a-118f are mapped as points on the first segment of the
quantization map. For example, if all DPAs 118a-118f output power
signals having 0.degree. phase, then the total power signal output
would have a weight of "6" since and each of the DPAs 118a-118f has
a weight of "1". However, if all of the DPAs 118a-118f are
inactive, then the output would be 0 since no DPAs would output a
power signal with a weight of "1." If five DPAs 118, such as the
DPAs 118a-118e are inactive and one DPA, such as DPA 118f, outputs
a power signal at .theta., then the total power signal output would
be a quantization point "1" from the origin at an angle .theta.
because there is only a single power signal being output with the
power signal being located at an angle .theta. and having a weight
"1." Once all of the points are mapped for the first segment, the
first segment is rotated by the angle .theta. and copied. The
process is repeated until 360.degree. is covered to form the
equal-weight quantization map as shown in FIG. 6. The equal-weight
quantization map can be pre-stored in the signal processor 104 and
more specifically, the quantizer 130. The equal-weight quantization
map 130 can be used to map the signals I_ns and Q_ns to determine
the quantized signals I_.DELTA..SIGMA. and Q_.DELTA..SIGMA. which
should be output by the quantizer 130 as seen in FIG. 7 and FIG.
8.
[0071] To determine the quantized signals I_.DELTA..SIGMA. and
Q_.DELTA..SIGMA. which should be output, the signal processor 104
and/or the quantizer 130 can perform a process according to FIG. 9
with reference to FIG. 7 and FIG. 8. In Step 5902, an inner product
can be performed to determine a segment. For example,
P_k=I_ns*u_k+Q_ns*v_k, where (u_k,v_k) is the k-th segment, can be
computed as partially illustrated in FIG. 7. P_m can be found,
which is the largest amongst all P_k. In Step S904, rotation can be
performed. For example, the point (I_ns,Q_ns) can be rotated
clockwise by the angle (m-1)*.theta. to get (I_r,Q_r), which is in
the first segment. In Step S906, the closest quantization point can
be found. For example, coordinates can be found. Thus, the
coordinates f_1 and f_2 can be found such that
(I_r,Q_r)=f_1*(a0,0)+f_2*(a1,b1). Furthermore, a quantization point
can be mapped. For example, out of the four points that enclose
(I_r,Q_r):
floor(f.sub.--1)*(a0,0)+floor(f.sub.--2)*(a1,b1);
floor(f.sub.--1)*(a0,0)+ceil(f.sub.--2)*(a1,b1);
ceil(f.sub.--1)*a(0,0)+floor(f.sub.--2)*(a1,b1); and
ceil(f.sub.--1)*(a0,0)+ceil(f.sub.--2)*(a1,b1)
the closest point to (I_r,Q_r) should be found. The closest point
can be called, for example, (I_f,Q_f). In one embodiment, the
quantization point with the closest Euclidian distance to the point
indicated by the noise shaped baseband signals (I_ns, Q_ns) can be
found through brute force or any other acceptable methods. In Step
S908, counter-rotation can be performed. For example, the point
(I_f,Q_f) can be rotated counter-clockwise by the angle
(m-1)*.theta. to get the point (I_.DELTA..SIGMA.,
Q_.DELTA..SIGMA.). The signals I_.DELTA..SIGMA. and
Q_.DELTA..SIGMA. can then be output by the quantizer 130.
[0072] Using the quantization map, a quantization table can be
formulated. The quantization table can be used by the DPA control
mapper 106 to determine the value of the control signals sent to
each of the phase selectors 116. The value of the control signals
determines whether the phase selector outputs an inactive signal,
or one of the waveforms at the carrier frequency. The value of the
control signals also determines the phase of the waveforms at the
carrier frequency. The output of the phase selectors 116 determines
the power signal output of the DPAs 118. The quantization table can
include all of the points in the quantization map and the
corresponding control signal to send to each phase selector. For an
equal-weight quantization map, an equal-weight quantization table
can be formulated. The equal-weight quantization table can be used
by the DPA control mapper 106 to determine the values of the
control signals C_1-C_6 to send to each of the phase selectors
116a-116f in FIG. 4. As previously noted, the value of the control
signals determines whether the phase selectors 116a-116f output an
inactive signal or a waveform at a carrier frequency with a phase.
The value of the control signals also indicate the phase of the
waveform output by each of the phase selectors 116a-116f to the
corresponding DPAs 118a-118f in FIG. 4.
[0073] FIG. 10 depicts a control signal table used by the DPA
control mapper 106 and/or the phase selectors 116 to code or decode
the values of the control signals. For example, a control signal
having a value 0 indicates that the phase selector should output an
inactive signal. However, a control signal having a value 1
indicates that the phase selector should output a waveform at a
carrier frequency having a phase of 0.degree.. Furthermore the
control signals having values of 2-8 indicates that the phase
selector should output a waveform at a carrier frequency having a
phase which is a multiple of .theta..
[0074] FIGS. 11, 13, and 15 depict three equal-weight quantization
tables which correspond to points shown in the maps of FIGS. 12,
14, and 16, respectively. Although the equal-weight quantization
tables are split into three tables, they can all be combined into a
single table. Furthermore, although the three equal-weight
quantization tables indicate only 25 quantization points and their
corresponding control signals, all of the quantization points can
be indicated in one or more equal-weight quantization tables.
[0075] The equal-weight quantization tables list the quantization
point and the corresponding values of the control signals. For
example, for the quantization point (6,0), the corresponding value
of the control signals should be C_1=1, C_2=1, C_3=1, C_4=1, C_5=1,
and C_6=1 as indicated in FIG. 11. Using the control signal table
shown in FIG. 10, the control signals indicate that the phase
selector 116a should output a waveform with having a 0.degree.
phase, the phase selector 116b should output a waveform having a
0.degree. phase, the phase selector 116c should output a waveform
having a 0.degree. phase, the phase selector 116d should output a
waveform having a 0.degree. phase, the phase selector 116e should
output a waveform having a 0.degree. phase, and the phase selector
116f should output a waveform having a 0.degree. phase.
[0076] Likewise, for the quantization point (4.2, 4.2), the value
of the control signals should be C_1=2, C_2=2, C_3=2, C_4=2, C_5=2,
and C_6=2 as indicated in FIG. 11. Using the control signal table
shown in FIG. 10, the control signals indicate that the phase
selector 116a should output a waveform having a .theta. phase, the
phase selector 116b should output a waveform having a .theta.
phase, the phase selector 116c should output a waveform having a
.theta. phase, the phase selector 116d should output a waveform
having a .theta. phase, the phase selector 116e should output a
waveform having a .theta. phase, and the phase selector 116f should
output a waveform having a .theta. phase. The same analysis can be
performed for any of the quantization points in the equal-weight
quantization tables shown in FIGS. 13 and 15. The outputted
waveforms having the indicated phases will cause the DPAs 118a-118f
to output power signals at a carrier frequency with the
corresponding phases. The combiner 120 (FIG. 2) will combine the
power signals to form an output signal which is an approximation of
the baseband signals I_bb and Q_bb, but at the carrier frequency.
Although the above example uses a quantization table to determine
the value of the control signals sent to each of the phase
selectors, the methods for determining the value of the control
signals are not limited to using the quantization table described
above. Any other acceptable method can be used.
[0077] FIG. 17 is a PSD graph for the output signal of the
transmitter 200 according to an embodiment of the present
invention. In FIG. 17, the PSD for a Band 5 LTE signal at a carrier
frequency of 834 MHz with 6 DPAs is shown as the line labeled
"after up-conversion." As can be seen, the PSD is below the PSD
mask, which can be, for example, a PSD mask according to a
guideline. The guideline can be, for example, a guideline from any
organization such as the Third Generation Partnership Project
("3GPP"). Thus, the transmitter 200 can operate within the
guidelines set by the 3GPP. The guideline an also be a guidelines,
for example, from a governmental agency such as the Federal
Communications Commission ("FCC").
[0078] Advantageously the use of equal-weight mapping uses the same
DPA 118 size as linear PA solutions. Also, for every doubling in
the number of DPAs 118, there is a 6 dB improvement in power
spectral density, which is a 6 dB reduction in noise. Furthermore,
the smaller the .theta., the greater the number of quantization
points, and the lower the average Euclidian Distance between the
quantization points and the noise shaped baseband signal produced
by the noise shaper 128. By correlation there is a more accurate
representation of the baseband signal.
[0079] Instead of using equal-weight mapping, the present invention
can also use binary-weight mapping. In one embodiment, as shown in
FIG. 18, three phase selectors 116a-116c and three DPA 118a-118c
are used for the binary-weight mapping. Although three phase
selectors 116 and three DPAs 118 are shown in FIG. 18, the number
of phase selectors 116 and the number of DPAs 118 are merely
illustrative. Thus, any number of phase selectors 116 and any
number of DPAs 118 may be used. Furthermore, each of the DPAs
118a-118c has its weight displayed in parenthesis. In binary-weight
mapping, the weight of each DPA 118 is different and covers 2.sup.0
to 2.sup.n-1 where n is the number of DPAs 118. This can be seen by
DPA 118a having a weight of 2.sup.0 or "1," DPA 118b having a
weight of 2.sup.1 or "2," and DPA 118c having a weight of 2.sup.2
or "4" in FIG. 18.
[0080] When using binary-weight mapping, a binary-weight
quantization map should be utilized. To generate a binary-weight
quantization map, a first segment of the binary-weight quantization
map is generated as shown in FIG. 19. For binary-weight mapping,
each of the DPAs 118a-118c has a binary weight selected from
2.sup.0 to 2.sup.n-1 where n is the number of DPAs 118.
Furthermore, each of the DPAs 118a-118c can be inactive, output a
power signal at carrier frequency with a 0.degree. phase and a
binary weight, or output a power signal with a multiple of a
.theta. phase and a binary weight. In FIG. 19, .theta. is set to be
45.degree., however, the .theta. can be set at any angle. By
increasing the number of DPAs 118 used or reducing the .theta.
used, the noise in the PSD can be reduced because the number of
quantization points is increased. The increase in the number of
quantization points reduces noise in the PSD since the Euclidian
distance between the closest quantization point (I_.DELTA..SIGMA.
and Q_.DELTA..SIGMA.) and the noise shaped baseband signal (I_ns
and Q_ns) is generally decreased. This allows for a closer
approximation of the baseband signal (I_bb and Q_bb).
[0081] As seen in FIG. 19, all combinations of the power signal
outputs of the DPAs 118a-118c are mapped as quantization points on
the first segment of the quantization map. For example, if all DPAs
118a-118c output power signals having 0.degree. phase, then the
total power signal output would have a weight of "7" since the DPA
118a outputs a power signal with a weight of "1," the DPA 118b
outputs a power signal with a weight of "2," and the DPA 118c
outputs a power signal with a weight of "4." However, if all of the
DPAs 118a-118c are inactive, then the total power signal output
would be 0 since no DPAs would output a power signal with a binary
weight. If two DPAs 118, such as the DPAs 118a and 118b are
inactive and one DPA 118 such as the DPA 118c outputs a power
signal at .theta., then the total power signal output would be a
quantization point "4" from the origin at an angle .theta. because
there is only a single power signal being output with the power
signal being located at an angle .theta. and having a weight "4."
Once all of the points are mapped for the first segment, the first
segment is rotated by the angle .theta. and copied. The process is
repeated until 360.degree. is covered to form the binary-weight
quantization map as shown in FIG. 20. The binary-weight
quantization map can be pre-stored in the signal processor 104 and
more specifically, the quantizer 130. The binary-weight
quantization map 130 can be used to map the signals I_ns and Q_ns
to determine the quantized signals I_.DELTA..SIGMA. and
Q_.DELTA..SIGMA. which should be output by the quantizer 130 as
seen in FIG. 21 and FIG. 22.
[0082] To determine the quantized signals I_.DELTA..SIGMA. and
Q_.DELTA..SIGMA. which should be output, the signal processor 104
and/or the quantizer 130 can perform a process according to FIG. 9
with reference to FIG. 21 and FIG. 22. In Step S902, an inner
product can be performed to determine a segment. For example,
P_k=I_ns*u_k+Q_ns*v_k, where (u_k,v_k) is the bisector of the k-th
segment, can be computed as partially illustrated in FIG. 21. P_m
can be found, which is the largest amongst all P_k. In Step S904,
rotation can be performed. For example, the point (I_ns,Q_ns) can
be rotated clockwise by the angle (m-1)*.theta. to get (I_r,Q_r),
which is in the first segment. In Step S906, the closest
quantization point can be found. For example, the point (I_f,Q_f)
which is closest to the point (I_r,Q_r) is found. In one
embodiment, the quantization point with the closest Euclidian
distance to the point indicated by the noise shaped baseband
signals (I_ns, Q_ns) can be found through brute force or any other
acceptable methods. In Step S908, counter-rotation can be
performed. For example, the point (I_f,Q_f) can be rotated
counter-clockwise by the angle (m-1)*.theta. to get the point
(I_.DELTA..SIGMA., Q_.DELTA..SIGMA.). The signals I_.DELTA..SIGMA.
and Q_.DELTA..SIGMA. can then be output by the quantizer 130.
[0083] For a binary-weight quantization map, a binary-weight
quantization table can be formulated. The binary-weight
quantization table can be used by the DPA control mapper 106 to
determine the values of the control signals C_1-C_3 to send to each
of the phase selectors 116a-116c in FIG. 18. As previously noted,
the value of the control signals determines whether the phase
selectors 116a-116c output an inactive signal or a waveform at a
carrier frequency with a phase. The value of the control signals
also indicate the phase of the waveform output by each of the phase
selectors 116a-116c to the corresponding DPAs 118a-118c in FIG.
18.
[0084] FIG. 23 depicts a control signal table used by the DPA
control mapper 106 and/or the phase selectors 116 to code or decode
the values of the control signals. For example, a control signal
having a value 0 indicates that the phase selector should output an
inactive signal. However, a control signal having a value 1
indicates that the phase selector should output a waveform at a
carrier frequency having a phase of 0.degree.. Furthermore the
control signals having values of 2-8 indicates that the phase
selector should output a waveform at a carrier frequency having a
phase which is a multiple of .theta..
[0085] FIGS. 24, 26, and 28 depict three binary-weight quantization
tables which correspond to points shown in the maps of FIGS. 25,
27, and 29, respectively. Although the binary-weight quantization
tables are split into three tables, they can all be combined into a
single table. Furthermore, although the three binary-weight
quantization tables indicate only 25 quantization points and their
corresponding control signals, all of the quantization points can
be indicated in one or more binary-weight quantization tables.
[0086] The binary-weight quantization tables list the quantization
point and the corresponding values of the control signals. For
example, for the quantization point (7,0), the corresponding value
of the control signals should be C_1=1, C_2=1, and C_3=1, as
indicated in FIG. 24. Using the control signal table shown in FIG.
23, the control signals indicate that the phase selector 116a
should output a waveform with having a 0.degree. phase, the phase
selector 116b should output a waveform having a 0.degree. phase,
and the phase selector 116c should output a waveform having a
0.degree. phase.
[0087] Likewise, for the quantization point (4.9, 4.9), the value
of the control signals should be C_1=2, C_2=2, and C_3=2, as
indicated in FIG. 24. Using the control signal table shown in FIG.
23, the control signals indicate that the phase selector 116a
should output a waveform having a .theta. phase, the phase selector
116b should output a waveform having a .theta. phase, and the phase
selector 116c should output a waveform having a .theta. phase. The
same analysis can be performed for any of the quantization points
in the binary-weight quantization tables shown in FIGS. 26 and 28.
The outputted waveforms having the indicated phases will cause the
DPAs 118a-118c to output power signals at a carrier frequency with
the corresponding phases. The combiner 120 (FIG. 2) will combine
the power signals to form an output signal which is an
approximation of the baseband signals I_bb and Q_bb, but at the
carrier frequency. Although the above example uses a quantization
table to determine the value of the control signals sent to each of
the phase selectors, the methods for determining the value of the
control signals are not limited to using the quantization table
described above. Any other acceptable method can be used.
[0088] Advantageously the use of binary-weight mapping uses the
same DPA 118 size as linear PA solutions. In addition,
binary-weight mapping generally uses fewer DPAs 118 when compared
with equal-weight mapping. Furthermore, the smaller the 0, the
greater the number of quantization points, and the lower the
average Euclidian Distance between the quantization points and the
noise shaped baseband signal produced by the noise shaper 128. By
correlation there is a more accurate representation of the baseband
signal.
[0089] In one embodiment, as shown in FIG. 30, four phase selectors
116a-116d and four DPAs 118a-118d are used for the arbitrary-weight
mapping. Although four phase selectors 116 and four DPAs 118 are
shown in FIG. 30, the number of phase selectors 116 and the number
of DPAs are merely illustrative. Thus, any number of phase
selectors 116 and any number of DPAs 118 may be used. Furthermore,
each of the DPAs 118a-118d has its weight displayed in parenthesis.
In arbitrary-weight mapping, the weight of each DPA can be random,
as seen by the DPA 118a having a weight of "1," the DPA 118b having
a weight "2," the DPA 118c having a weight of "1" and the DPA 118d
having a weight of "2."
[0090] When using arbitrary-weight mapping, an arbitrary-weight
quantization map should be utilized. To generate an
arbitrary-weight quantization map, a first segment of the
arbitrary-weight quantization map is generated as shown in FIG. 31.
For arbitrary-weight mapping, each of the DPAs 118a-118d have an
arbitrary weight, which in this example is "1" or "2." Furthermore,
each of the DPAs 118a-118d can be inactive, output a power signal
at carrier frequency with a 0.degree. phase and the arbitrary
weight, or output a power signal with a multiple of a .theta. phase
and the arbitrary weight. In FIG. 31, .theta. is set to be
45.degree., however, the .theta. can be set at any angle. By
increasing the number of DPAs 118 used or reducing the .theta.
used, the noise in the PSD can be reduced because the number of
quantization points is increased. The increase in the number of
quantization points reduces noise in the PSD since the Euclidian
distance between the closest quantization point (I_.DELTA..SIGMA.
and Q_.DELTA..SIGMA.) and the noise shaped baseband signal (I_ns
and Q_ns) is generally decreased. This allows for a closer
approximation of the baseband signal (I_bb and Q_bb).
[0091] As seen in FIG. 31, all combinations of the states of the
DPAs 118a-118d are mapped as points on the first segment of the
quantization map. For example, if all DPAs 118a-118d output power
signals having 0.degree. phase, then the total power signal output
would have a weight of "6" since the DPA 118a would output a power
signal with a weight of "1," the DPA 118b would output a power
signal with a weight of "2," the DPA 118c would output a power
signal with a weight of "1," and the DPA 118d would output a power
signal with a weight of "2." However, if all of the DPAs 118a-118d
are inactive, then the output would be 0 since no DPAs would output
a power signal with any weight. If three DPAs 118, such as the DPAs
118a-118c are inactive and one DPA, such as DPA 118d, outputs a
power signal at .theta., then the total power signal output would
be a quantization point "2" from the origin at an angle .theta.
because there is only a single power signal being output with the
power signal being located at an angle .theta. and having a weight
"2." Once all of the points are mapped for the first segment, the
first segment is rotated by the angle .theta. and copied. The
process is repeated until 360.degree. is covered to form the
arbitrary-weight quantization map as shown in FIG. 32. The
arbitrary-weight quantization map can be pre-stored in the signal
processor 104 and more specifically, the quantizer 130. The
arbitrary-weight quantization map 130 can be used to map the
signals I_ns and Q_ns to determine the quantized signals
I_.DELTA..SIGMA. and Q_.DELTA..SIGMA. which should be output by the
quantizer 130 as seen in FIG. 33 and FIG. 34.
[0092] To determine the quantized signals I_.DELTA..SIGMA. and
Q_.DELTA..SIGMA. which should be output, the signal processor 104
and/or the quantizer 130 can perform a process according to FIG. 9
with reference to FIG. 33 and FIG. 34. In Step S902, an inner
product can be performed to determine a segment. For example,
P_k=I_ns*u_k+Q_ns*v_k, where (u_k,v_k) is the bisector of the k-th
segment, can be computed as partially illustrated in FIG. 33. P_m
can be found, which is the largest amongst all P_k. In Step S904,
rotation can be performed. For example, the point (I_ns,Q_ns) can
be rotated clockwise by the angle (m-1)*.theta. to get (I_r,Q_r),
which is in the first segment. In Step S906, the closest
quantization point can be found. For example, coordinates can be
found. Thus, the coordinates f_1 and f_2 can be found such that
(I_r,Q_r)=f_1*(a0,0)+f_2*(a1,b1). Furthermore, a quantization point
can be mapped. For example, out of the four points that enclose
(I_r,Q_r):
floor(f.sub.--1)*(a0,0)+floor(f.sub.--2)*(a1,b1);
floor(f.sub.--1)*(a0,0)+ceil(f.sub.--2)*(a1,b1);
ceil(f.sub.--1)*a(0,0)+floor(f.sub.--2)*(a1,b1); and
ceil(f.sub.--1)*(a0,0)+ceil(f.sub.--2)*(a1,b1)
the closest point to (I_r,Q_r) should be found. The closest point
can be called, for example, (I_f,Q_f). In one embodiment, the
quantization point with the closest Euclidian distance to the point
indicated by the noise shaped baseband signals (I_ns, Q_ns) can be
found through brute force or any other acceptable methods. In Step
S908, counter-rotation can be performed. For example, the point
(I_f,Q_f) can be rotated counter-clockwise by the angle
(m-1)*.theta. to get the point (I_.DELTA..SIGMA.,
Q_.DELTA..SIGMA.). The signals I_.DELTA..SIGMA. and
Q_.DELTA..SIGMA. can then be output by the quantizer 130.
[0093] For an arbitrary-weight quantization map, an
arbitrary-weight quantization table can be formulated. The
arbitrary-weight quantization table can be used by the DPA control
mapper 106 to determine the values of the control signals C_1-C_4
to send to each of the phase selectors 116a-116d in FIG. 30. As
previously noted, the value of the control signals determines
whether the phase selectors 116a-116d output an inactive signal or
a waveform at a carrier frequency with a phase. The value of the
control signals also indicate the phase of the waveform output by
each of the phase selectors 116a-116d to the corresponding DPAs
118a-118d in FIG. 30.
[0094] FIG. 35 depicts a control signal table used by the DPA
control mapper 106 and/or the phase selectors 116 to code or decode
the values of the control signals. For example, a control signal
having a value 0 indicates that the phase selector should output an
inactive signal. However, a control signal having a value 1
indicates that the phase selector should output a waveform at a
carrier frequency having a phase of 0.degree.. Furthermore the
control signals having values of 2-8 indicates that the phase
selector should output a waveform at a carrier frequency having a
phase which is a multiple of .theta..
[0095] FIGS. 36, 38, and 40 depict three arbitrary-weight
quantization tables which correspond to points shown in the maps of
FIGS. 37, 39, and 41, respectively. Although the arbitrary-weight
quantization tables are split into three tables, they can all be
combined into a single table. Furthermore, although the three
arbitrary-weight quantization tables indicate only 25 quantization
points and their corresponding control signals, all of the
quantization points can be indicated in one or more
arbitrary-weight quantization tables.
[0096] The arbitrary-weight quantization tables list the
quantization point and the corresponding values of the control
signals. For example, for the quantization point (6,0), the
corresponding value of the control signals should be C_1=1, C_2=1,
C_3=1, and C_4=1 as indicated FIG. 36. Using the control signal
table shown in FIG. 35, the control signals indicate that the phase
selector 116a should output a waveform with having a 0.degree.
phase, the phase selector 116b should output a waveform having a
0.degree. phase, the phase selector 116c should output a waveform
having a 0.degree. phase, and the phase selector 116d should output
a waveform having a 0.degree. phase
[0097] Likewise, for the quantization point (4.2, 4.2), the value
of the control signals should be C_1=2, C_2=2, C_3=2, and C_4=2 as
indicated in FIG. 36. Using the control signal table shown in FIG.
35, the control signals indicate that the phase selector 116a
should output a waveform having a .theta. phase, the phase selector
116b should output a waveform having a .theta. phase, the phase
selector 116c should output a waveform having a .theta. phase, and
the phase selector 116d should output a waveform having a .theta.
phase. The same analysis can be performed for any of the
quantization points in the arbitrary-weight quantization tables
shown in FIG. 38 and FIG. 40. The outputted waveforms having the
indicated phases will cause the DPAs 118a-118d to output power
signals at a carrier frequency with the corresponding phases. The
combiner 120 (FIG. 2) will combine the power signals to form an
output signal which is an approximation of the baseband signals
I_bb and Q_bb, but at the carrier frequency. Although the above
example uses a quantization table to determine the value of the
control signals sent to each of the phase selectors, the methods
for determining the value of the control signals are not limited to
using the quantization table described above. Any other acceptable
method can be used.
[0098] Advantageously the use of arbitrary-weight mapping uses the
same DPA 118 size as linear PA solutions. Also, depending on the
weights assigned to the DPAs, for every doubling in the number of
DPAs 118, there may be a 6 dB improvement in power spectral
density, which is a 6 dB reduction in noise. Furthermore, the
smaller the .theta., the greater the number of quantization points,
and the lower the average Euclidian Distance between the
quantization points and the noise shaped baseband signal produced
by the noise shaper 128. By correlation there is a more accurate
representation of the baseband signal.
[0099] FIG. 42 depicts a transmitter 300 according to another
embodiment of the present invention. As seen in FIG. 42, the
quantized signals I_.DELTA..SIGMA. and Q_.DELTA..SIGMA. are
separately converted to the carrier frequency. The DPA control
mapper 106 is replaced by a DPA control mapper 306. The DPA control
mapper 306 receives the quantized signals I_.DELTA..SIGMA. and
Q_.DELTA..SIGMA. and generates two sets of control signals, I_1-I_n
and Q_1-Q_n. The phase selection array 108 is replaced by the phase
selection array 142 and the phase selection array 144. Furthermore,
the DPAs 118 are replaced by the DPAs 146 and 148.
[0100] The phase selection array 142 receives the control signals
I_1-I_n and outputs either an inactive signal or a plurality of
waveforms at a carrier frequency having a phase .theta.. The
waveforms from the phase selection array 142 are received by the
DPAs 146. In response to the inactive signal or the plurality of
waveforms from the phase selection array 142, the DPAs 146 output a
plurality of power signal outputs with waveforms having phases
corresponding to the phases of the control signals. The oscillator
115 is replaced by the oscillator 315 and the phases output by the
oscillator 315 can be limited to a small subset specific to the
mapping technique. For example, for grid mapping the phases can be
either 0.degree., 90.degree., 180.degree., or 270.degree.. The
combined power signal from the DPAs 146 reproduces the quantized
signal I_.DELTA..SIGMA. and approximates the baseband signal I_bb,
but at the carrier frequency.
[0101] The phase selection array 144 receives the control signals
Q_1-Q_n and outputs either an inactive signal or a plurality of
waveforms at a carrier frequency having a phase .theta.. The
waveforms from the phase selection array 144 are received by the
DPAs 148. In response to the inactive signal or the plurality of
waveforms from the phase selection array 144, the DPAs 148 output a
plurality of power signal outputs with waveforms having phases
corresponding to the phases of the control signals. The combined
power signal from the DPAs 148 reproduces the quantized signal
Q_.DELTA..SIGMA. and approximates the baseband signal Q_bb, but at
the carrier frequency. The transmitter 300 can be used, for
example, for mapping techniques where separation of the I_bb and
Q_bb signals are desirable, such as for grid mapping.
[0102] As seen in FIG. 43, quantization points can be mapped using
grid mapping to develop a grid mapping quantization map. The grid
mapping quantization map may be used, for example, by the
transmitter 300 and more specifically, the quantizer 130 during
grid mapping. In grid mapping, the quantization points are arranged
in a grid-like manner such that lines can be drawn connecting the
quantization points to form a grid. In grid mapping, the
I_.DELTA..SIGMA. values approximate the X value in a Cartesian
coordinate system while the Q_.DELTA..SIGMA. values approximate the
Y value in the Cartesian coordinate system. For grid mapping, as
shown in FIG. 42, the DPAs 146 and 148 are also binary weighted.
However, the DPAs 146 and 148 can also be equal-weighted and/or
arbitrary-weighted.
[0103] FIG. 44 depicts a control signal table for grid mapping used
by the DPA control mapper 306 and/or the phase selectors in the
phase selection array 142 to code or decode the values of the
control signals I_1 to I_n. For example, a control signal having a
value 0 indicates that the phase selector should output an inactive
signal. However, a control signal having a value 1 indicates that
the phase selector should output a waveform at a carrier frequency
having a phase of 0.degree.. Furthermore the control signals having
a value of 2 indicates that the phase selector should output a
waveform at a carrier frequency having a phase 180.degree..
[0104] FIG. 45 depicts a grid mapping quantization table for the
DPA control mapper 306 and/or the phase selection array 142. In
FIG. 45, a.sub.1 to a.sub.n is the binary representation of the
quantized value for the input absolute value of I_.DELTA..SIGMA..
Each a.sub.k can be either 0 or 1. When a.sub.k is equal to 0, the
output I_k for a phase selector in the phase selection array 142
should be an inactive signal. However, when a.sub.k is equal to 1
and the value of I_.DELTA..SIGMA. is positive, the phase selector
output should be a waveform at a carrier frequency having a phase
of 0.degree.. Likewise, when a.sub.k is equal to 1 and the value of
I_.DELTA..SIGMA. is negative, the phase selector output should be a
waveform at a carrier frequency having a phase of 180.degree..
[0105] FIG. 46 depicts a control signal table for grid mapping used
by the DPA control mapper 306 and/or the phase selectors in the
phase selection array 144 to code or decode the values of the
control signals Q_1 to Q_n. For example, a control signal having a
value 0 indicates that the phase selector should output an inactive
signal. However, a control signal having a value 1 indicates that
the phase selector should output a waveform at a carrier frequency
having a phase of 90.degree.. Furthermore the control signals
having a value of 2 indicates that the phase selector should output
a waveform at a carrier frequency having a phase 270.degree..
[0106] FIG. 47 depicts a grid mapping quantization table for the
DPA control mapper 306 and/or the phase selection array 144. In
FIG. 47, b.sub.1 to b.sub.n is the binary representation of the
quantized value for the input absolute value of Q_.DELTA..SIGMA..
Each b.sub.k can be either 0 or 1. When b.sub.k is equal to 0, the
output Q_k, for a phase selector in the phase selection array 144
should be an inactive signal. However, when b.sub.k is equal to 1
and the value of Q_.DELTA..SIGMA. is positive, the phase selector
output should be a waveform at a carrier frequency having a phase
of 90.degree.. Likewise, when b.sub.k is equal to 1 and the value
of Q_.DELTA..SIGMA. is negative, the phase selector output should
be a waveform at a carrier frequency having a phase of 270.degree..
Although the above example uses a quantization table to determine
the value of the control signals sent to each of the phase
selectors, the methods for determining the value of the control
signals are not limited to using the quantization table described
above. Any other acceptable method can be used.
[0107] FIG. 48 is a PSD graph for the output signal of the
transmitter 300 using the grid mapping. In FIG. 48, the PSD for a
Band 5 LTE signal at a carrier frequency of 834 MHz with 6 DPAs is
shown as the line labeled "after up-conversion." As can be seen,
the PSD is below the PSD mask, which can be, for example, a PSD
mask according to a guideline. The guideline can be, for example, a
guideline from any organization such as the 3GPP. Thus, the
transmitter 300 can operate within the guidelines set by the 3GPP.
The guideline an also be a guidelines, for example, from a
governmental agency such as the FCC.
[0108] Advantageously the use of grid mapping uses a relatively
non-intensive quantization algorithm to produce the quantization
map and the quantization table. Also, for every additional DPAs of
binary weight added to the DPAs 146 and 148, there is a 6 dB
improvement in power spectral density, which is a 6 dB reduction in
noise. Furthermore, the grid mapping uses a relatively non-complex
input drive stage for each DPAs 146 and 148.
[0109] With the present invention, the mapping technique can be
selected according to a desire for noise reduction, manufacturing
costs, and/or processing power required to implement the mapping
technique. Furthermore, although only examples for equal-weight
mapping, binary-weight mapping, arbitrary-weight mapping, and/or
grid mapping are disclosed, any other type of mapping techniques
may be used in order to achieve a high-efficiency transmitter which
is not susceptible to the mismatch problems from a supply
modulator.
[0110] Those of ordinary skill would appreciate that the various
illustrative logical blocks, modules, and algorithm steps described
in connection with the examples disclosed herein may be implemented
as electronic hardware, computer software, or combinations of both.
Furthermore, the present invention can also be embodied on a
machine readable medium causing a processor or computer to perform
or execute certain functions.
[0111] To clearly illustrate this interchangeability of hardware
and software, various illustrative components, blocks, modules,
circuits, and steps have been described above generally in terms of
their functionality. Whether such functionality is implemented as
hardware or software depends upon the particular application and
design constraints imposed on the overall system. Skilled artisans
may implement the described functionality in varying ways for each
particular application, but such implementation decisions should
not be interpreted as causing a departure from the scope of the
disclosed apparatus and methods.
[0112] The various illustrative logical blocks, units, modules, and
circuits described in connection with the examples disclosed herein
may be implemented or performed with a general purpose processor, a
digital signal processor (DSP), an application specific integrated
circuit (ASIC), a field programmable gate array (FPGA) or other
programmable logic device, discrete gate or transistor logic,
discrete hardware components, or any combination thereof designed
to perform the functions described herein. A general purpose
processor may be a microprocessor, but in the alternative, the
processor may be any conventional processor, controller,
microcontroller, or state machine. A processor may also be
implemented as a combination of computing devices, e.g., a
combination of a DSP and a microprocessor, a plurality of
microprocessors, one or more microprocessors in conjunction with a
DSP core, or any other such configuration.
[0113] The steps of a method or algorithm described in connection
with the examples disclosed herein may be embodied directly in
hardware, in a software module executed by a processor, or in a
combination of the two. The steps of the method or algorithm may
also be performed in an alternate order from those provided in the
examples. A software module may reside in RAM memory, flash memory,
ROM memory, EPROM memory, EEPROM memory, registers, hard disk, a
removable disk, a CD-ROM, or any other form of storage medium known
in the art. An exemplary storage medium is coupled to the processor
such that the processor can read information from, and write
information to, the storage medium. In the alternative, the storage
medium may be integral to the processor. The processor and the
storage medium may reside in an Application Specific Integrated
Circuit (ASIC). The ASIC may reside in a wireless modem. In the
alternative, the processor and the storage medium may reside as
discrete components in the wireless modem.
[0114] The previous description of the disclosed examples is
provided to enable any person of ordinary skill in the art to make
or use the disclosed methods and apparatus. Various modifications
to these examples will be readily apparent to those skilled in the
art, and the principles defined herein may be applied to other
examples without departing from the spirit or scope of the
disclosed method and apparatus. The described embodiments are to be
considered in all respects only as illustrative and not restrictive
and the scope of the invention is, therefore, indicated by the
appended claims rather than by the foregoing description. All
changes which come within the meaning and range of equivalency of
the claims are to be embraced within their scope.
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